Soldering technologies using a laser beam are well known and disclosed in, for example, the following Patent Documents 1 or 2. In the technologies, the laser beam is projected on a to-be-soldered object such as a printed circuit bard from a soldering head, and a solder is melted with heat of the laser beam, so that soldering can be performed. Therefore, these technologies have an advantage in that the soldering can be performed in a non-contact manner.
However, conventionally, as shown in FIGS. 7 and 8, by projecting a circular laser beam 2 on a to-be-soldered object 3 in a spot shape by a soldering head, a threadlike solder 8 supplied from a nozzle 7 is melted and the soldering is performed. Therefore, in a case where the to-be-soldered object 3 is a annular terminal 4a provided to a board 4 and a bar-shaped terminal 5a of a electronic part inserted therein, the laser beam 2 may be projected on the electronic part 5 through a clearance 6 between the annular terminal 4a and the bar-shaped terminal 5a, so that a portion of the electronic part 5 may be burnt disadvantageously.
In addition, in Patent Documents 3 and 4, disclosed are technologies for heating and machining a to-be-soldered object by using a ring shape laser beam. If the soldering of the annular terminal 4a and the bar-shaped terminal 5a is performed by using such a ring shape laser beam, the aforementioned problem of the burning of the electronic part may be solved.
Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 4-52073
Patent Document 2: JP-A No. 2002-1521
Patent Document 3: JP-A No. 2005-28428
Patent Document 4: JP-A No. 2006-229075
However, the ring shape laser beam can heat only the annular terminal 4a. That is, the bar-shaped terminal 5a disposed at the central portion cannot be heated. Therefore, the melted solder is rapidly cooled down by a low temperature of the bar-shaped terminal 5a. As a result, the soldering deteriorates, and soldering time is increased, so that work efficiency is lowered. Particularly, in a case where the many soldering points are consecutively soldered by a soldering robot, the entire work efficiency is greatly lowered.